JPH08290521A - Heat-sensitive adherent resin coated metal plate and manufacture thereof and bonding method therebetween - Google Patents

Abstract

PURPOSE: To obtain excellent bonding force by being heated to comparatively low temperature and for short period of time and pressurized under the condition that surfaces to be bonded are brought into close contact with each other by a method wherein the surface of metal plate is coated with a paint film containing a water-soluble or water-dispersible thermoplastic resin having a reactive functional group and a crosslinker. CONSTITUTION: This heat-sensitive adherent resin coated metal plate is obtained by coating the surface of the metal plate with a paint film containing a water- soluble or water-dispersible thermoplastic resin A having a reactive functional group and a crosslinker B and then dried under the temperature condition that no crosslinking reaction develops between the thermoplastic resin A and the crosslinker B. In this case, the thermoplastic resin A to be employed is one or two and more among a polyethylene-based resin, a polyester-based resin and a polyurethane-based resin having a functional group, which reacts with a melamine resin or with an isocyanate group. Further, the crosslinker B is a melamine resin having an active methylol group or blocked isocyanate group- containing compound.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a heat-sensitive adhesive type resin-coated metal plate, a method for producing the same, and a method for joining the resin-coated metal plates. It can be applied as an outer plate material for electric products, steel furniture, etc., or for building materials, etc., without the need for welding, adhesives, etc.
Or metal and non-metal plate (plywood plate, plastic plate,
(Including a rubber plate, cloth, etc.) can be easily joined.

[0002]

2. Description of the Related Art Welding methods, mechanical joining methods using bolts and nuts, etc.
A method using an adhesive including brazing is often used. On the other hand, what is adopted when joining a non-metallic material such as plastic, cloth, and plywood to a metallic plate is the bonding using an adhesive.

Base resins for adhesives used for adhesive bonding are roughly classified into thermoplastic resins, thermosetting resins and elastomers according to their thermal properties. Then, in the joining method using an adhesive, the adhesive is applied to one surface or both surfaces of the surface to be joined, and the components contained in the resin involved in the adhesion are reacted, or the resin is melted to improve the tackiness. In order to develop, the adherend is often heated and then pressure-bonded.

However, in such a joining method, a metal plate is first punched or sheared into a desired shape and then formed into a desired shape, and then an adhesive is individually applied to the surfaces of the portions to be joined. Therefore, the work efficiency is extremely poor, resulting in a decrease in productivity and an increase in manufacturing cost.

In addition, since the adhesive used often uses an organic solvent for adjusting the viscosity at the time of application, the organic solvent that volatilizes in the working environment may cause health problems,
Furthermore, there are dangers such as explosion and fire. Therefore, it is indispensable to install a centralized ventilation device in the adhesive application / bonding / assembly line, which causes an increase in equipment cost. It is also pointed out that since the viscosity of the adhesive agent is likely to fluctuate as the solvent volatilizes, the amount of the adhesive agent applied varies, resulting in difficulty in obtaining uniform adhesive strength.

Therefore, as means for solving the problems associated with the use of such organic solvents, for example, Japanese Patent Publication No. 52-
No. 8998 discloses an electromagnetic steel sheet for laminated iron cores of electric products, in which a thermoplastic resin and a thermosetting resin are diluted and mixed with an organic solvent, and an aqueous resin solution obtained by emulsifying this into an aqueous emulsion is applied to the surface of the steel sheet. And dried resin-coated electrical steel sheet is disclosed.

Since the resin-coated steel plates can be joined to each other only by superposing the adherends on each other and heating and pressurizing them, it is not necessary to separately apply an adhesive, so that the adhesive on the user side is not required. This has the advantage that the coating process can be omitted. It should be noted that it is difficult to obtain sufficient adhesive strength with a coating made of only a thermoplastic resin, and in particular, when the laminated iron core heats up to a high temperature during use, the adhesive plasticizes and the adhesive strength sharply decreases. In order to solve the problem, in the present publication, while increasing the heat resistance after joining by mixing a thermosetting resin with a thermoplastic resin, the softening point caused by the use of an emulsifier is also suppressed from decreasing, and the adhesive strength at high temperature is reduced. Is also suppressed.

However, as long as the thermoplastic resin is present in the coating film, it is unavoidable that the adhesive strength is reduced at high temperatures and in a wet environment, and the solvent resistance is also poor. In addition, in the resin-coated steel sheet described in this publication, the bonding work takes a long time, so that the efficiency of the bonding work is poor. For these reasons, the resin-coated steel sheet for iron core as described in this publication cannot be put to practical use as a structural material such as automobiles, home electric appliances, steel furniture or building materials.

Further, as a resin-coated steel sheet for laminated iron cores of the same type as described above, Japanese Patent Publication No. 52-8999 discloses a water-based acrylic resin emulsion mixed with an aqueous phenolic resin or an aqueous melamine resin. A method of obtaining an organic coated electromagnetic steel sheet by incomplete baking is disclosed, and this coated steel sheet can also be joined without application of an adhesive like the resin coated steel sheet described in the above publication. But,
Even with this product, the thermoplastic resin component remains in the coating film after adhesion, so if exposed to high-temperature conditions above the plasticization temperature or in a humid environment, a decrease in adhesive strength cannot be avoided, and solvent resistance Inferior to

Further, according to this publication, since incomplete baking for forming a bonding film is performed at a high temperature of 250 ° C. or higher at a short time, heating unevenness occurs in the baking process, and the resin locally deteriorates due to heat and adheres. In addition to large variations in strength, it is very difficult to control the baking temperature during joining. Therefore,
It is difficult to put such a resin-coated steel sheet for a laminated iron core into practical use as it is for automobiles, home electric appliances, steel furniture, or building materials.

Further, in JP-B-55-9825, a water-based emulsion of acrylic resin is disclosed in JP-B-55-9825, in which the temperature range and time at the time of baking in the incomplete baking method disclosed in the above publication are expanded to make the production easier. There is disclosed a self-adhesive resin-coated steel sheet obtained by applying a treatment liquid prepared by mixing a water-soluble styrene-maleic acid copolymer to the surface of a steel sheet to be treated and drying it. However, even with this resin coating, the adhesive strength at high temperature is slightly improved, and since it is basically a mixed coating film containing a thermoplastic resin, the adhesive strength at high temperature or in a wet environment is Insufficient and poor solvent resistance.

Further, in this publication, it is described that the adhesive strength is increased by the cross-linking bond between the acrylic resin and the water-soluble styrene-maleic acid copolymer. The bond of is not so strong, and since the styrene-maleic acid copolymer becomes a huge polymer, the fluidity becomes worse, and the bonding opportunity (crosslinking point) with the acrylic resin decreases.
No significant effect can be expected in improving the adhesive strength. Furthermore, the problem that the time required for bonding the laminated plates is long and the work efficiency at the time of bonding is poor remains unsolved.

[0013]

SUMMARY OF THE INVENTION The present invention has been made by paying attention to the above-mentioned circumstances, and its purpose is not limited to the kind and thickness of the metal plate, and the brazing and bonding. It does not require a joining means such as agent coating, and the surfaces to be joined can be brought into close contact with each other to obtain an excellent joining force by heating and pressurizing at a relatively low temperature for a short time. Furthermore, after joining, excellent adhesion durability To provide a resin-coated metal sheet having excellent heat-sensitive adhesiveness and capable of exhibiting heat resistance, heat-resistant adhesiveness, corrosion resistance, and solvent resistance, and a method for joining the resin-coated metal sheet together. It is what

[0014]

The constitution of the heat-sensitive adhesive coated metal plate according to the present invention which has been able to solve the above-mentioned problems is such that the surface of the metal plate is water-soluble or water-dispersible having a reactive functional group. The gist is that it is coated with a coating film containing the thermoplastic resin (A) and the crosslinking agent (B). The preferred thermoplastic resin (A) used here is one having a functional group which is plasticized at a temperature of 80 ° C. or higher and exhibits cross-linking reactivity with a cross-linking agent at a plasticization temperature or higher, and more specifically, Polyethylene resin, polyester resin having a functional group exhibiting cross-linking reactivity with melamine resin or cross-linking reactivity with isocyanate group,
Polyurethane resins can be mentioned, and preferred crosslinking agents (B) are those exhibiting crosslinking reactivity at 80 ° C. or higher,
More specifically, a melamine resin or a blocked isocyanate group-containing compound may be mentioned.

In the above, the preferred functional group exhibiting crosslinking reactivity with the melamine resin contained in the thermoplastic resin (A) is a hydroxyl group and / or a carboxyl group, and the preferred functional group exhibiting crosslinking reactivity with an isocyanate group is ,
One or more selected from the group consisting of a hydroxyl group, an amino group and a carboxyl group. The thermoplastic resin (A) is plasticized in a temperature range of 80 to 200 ° C., and the thermoplastic resin (A) and the cross-linking agent (B) are 230 ° C. or higher than the plasticizing temperature of the thermoplastic resin (A). Those that cause a cross-linking reaction in the following temperature range are particularly preferable, and the preferable adhesion amount of the coating film containing the thermoplastic resin (A) and the cross-linking agent (B) is 0.5 to 60 g / m ² in terms of solid content. is there.

Further, in producing the above-mentioned coated metal plate, after applying the coating liquid containing the thermoplastic resin (A) and the cross-linking agent (B) to the surface of the metal material whose surface has been cleaned, The drying may be performed under a temperature condition in which (A) and (B) do not cause a crosslinking reaction. Further, the joining method according to the present invention,
The heat-sensitive adhesive resin-coated metal plates obtained by the above-mentioned method or the heat-sensitive adhesive resin-coated metal plates are overlapped with each other, and a coating film containing a thermoplastic resin (A) and a crosslinking agent (B) is plasticized. 250 ° C or higher, which is the temperature above
It is performed by baking and joining at the following temperatures.

In the present invention, since the resin constituting the heat-sensitive bonding layer is water-soluble or water-dispersible, there is a risk of health hazard to workers, fire and explosion due to volatilization of the organic solvent in the coating and drying process. Moreover, since the evaporation of the solvent in the coating liquid and the solid content concentration and viscosity change accompanying it are small, the coating amount of the resin liquid is stable and a reliable and stable bonding state can be obtained.

[0018]

As described above, the resin-coated metal sheet excellent in heat-sensitive adhesiveness according to the present invention is preferably a thermoplastic resin having a functional group which is plasticized at a temperature of 80 ° C. or higher and causes a crosslinking reaction at the plasticization temperature or higher. A metal plate surface is coated with a resin (A) and a coating film containing, as a main component, a crosslinking agent (B) that causes a crosslinking reaction at a temperature of 80 ° C. or higher, and the coating film is formed. The plasticizing temperature of the thermoplastic resin (A) is 80 to 200.
It is preferable that the thermoplastic resin (A) and the crosslinking agent (B) exhibit a crosslinking reaction in the range of the plasticizing temperature of the thermoplastic resin (A) to 230 ° C. inclusive. .

Specific examples of the cross-linking agent (B) satisfying these preferable requirements include a melamine resin and a blocked isocyanate group-containing compound, and specific examples of the thermoplastic resin (A) include the above-mentioned melamine resin. Examples thereof include a polyethylene-based resin, a polyurethane-based resin, or a polyester-based resin having a cross-linking reactivity or a functional group having a cross-linking reactivity with an isocyanate group.

The resin-coated metal sheet according to the present invention has no stickiness or blocking property on the coated surface in the state of the cut plate or the coil product as it is, and is excellent in workability as well. The coating film constituent material has thermoplasticity and cross-linking reactivity in a state that the coating film surface does not have a processing flaw during punching and molding, and the coating film surfaces or the coating surface and the adherend surface are in close contact with each other. By heating to a temperature at which both of the above occur and baking is performed, it is possible to firmly bond the coating surfaces or the coating surface and the adherend surface.

The coating film before heating and baking has thermoplasticity and an appropriate hardness necessary for processing, but the coating film surface or the coating surface and the adherend surface were heated and baked together. After that,
Thermoplasticity disappears due to mutual cross-linking reaction between the functional groups in the resin that constitutes the coating film, and a strong adhesive strength between coating films is developed, as well as excellent performance in solvent resistance, corrosion resistance, and high temperature adhesive strength. Will be demonstrated.

The inventors of the present invention have no tackiness or tackiness after coating and drying, but by applying the coating surfaces to each other or the coating surface and the adherend surface, and baking at a predetermined temperature. For the first time, we have earnestly conducted research to obtain a resin coating film capable of exhibiting an adhesive effect. As a result, 8
Thermoplastic resin (A) which is plasticized at a temperature of 0 ° C. or higher and exhibits crosslinking reactivity at a temperature of 0 ° C. or higher [preferably, the plasticization temperature is 80 to 200 ° C. and the plasticization temperature is 230 ° C. or higher.
Thermoplastic resin showing cross-linking reactivity in the following temperature range, specifically, polyethylene-based resin or polyurethane-based resin having a functional group showing cross-linking reactivity with melamine resin or cross-linking reactivity with isocyanate group Or one or more polyester resins] and a thermosensitive crosslinking agent (B) which exhibits crosslinking reactivity at a temperature of 80 ° C. or higher [preferably not less than the plasticizing temperature of the thermoplastic resin (A) 23
A coating film mainly composed of a cross-linking agent showing cross-linking reactivity in a temperature range of 0 ° C. or lower, specifically, a melamine resin or a compound containing a blocked isocyanate group] has a heat-sensitive adhesive property of excellent characteristics that meets the above-mentioned demand. It became clear that it became a resin coating film layer. Hereinafter, the reasons for limitation and preferable modes of each component constituting the heat-sensitive adhesive resin-coated metal plate according to the present invention will be described in detail.

[Reason for Using Thermoplastic Resin (A)] First, the coated surfaces of the resin-coated metal plate or the coating surface and other adherend surfaces are brought into close contact with each other and then heated and baked to obtain a high adhesive strength. In order to achieve this, it is necessary that the resin coating film itself is once softened and exhibits fluidity in the initial stage of heating and baking. That is, the resin once softens under the heating at the beginning of baking, and in the case of joining the coating film surfaces, the adhesive surfaces are fused and integrated by the leveling action of the softened resin to form a smooth bonding surface. When joining a film surface to another adherend surface, the softened resin enters the irregularities of the other adherend surface to increase the contact area between the coating surface and the adherend surface, and to make it uniform over the entire joint surface. In addition, a strong joined state can be obtained. Therefore, as the main resin component constituting the coating film, it is essential to use the thermoplastic resin (A) which is plasticized in the initial stage of heating and baking.

[Plasticization temperature of thermoplastic resin (A)] The plasticization temperature of the thermoplastic resin (A) is preferably 80 ° C.
As mentioned above, the range of 80-200 degreeC is more preferable. The reason is as follows. That is, the metal plate itself is usually 10
Although it is heated to 0 ° C or higher, and more generally to about 100 to 250 ° C, in order to obtain sufficient adhesive strength after baking,
As described above, it is necessary that the resin coating film once softens and exhibits fluidity in the temperature range of the main baking. Therefore, the preferable plasticizing temperature of the resin (A) is 80 ° C. or higher, more preferably 80 to 200 ° C.

As will be described later, in the heating and baking step for joining, it is essential to heat to a temperature range where the functional groups in the resin cause a crosslinking reaction (thermal crosslinking reactivity developing temperature range). If the plasticizing temperature of the resin (A) is higher than the heating and baking temperature, the fluidity and leveling property of the resin (A) will not be exhibited during baking, resulting in insufficient homogenization and integration of the joint surface. As a result, satisfactory adhesiveness cannot be obtained. Therefore, the plasticizing temperature of the resin (A) is not higher than the crosslinkability manifesting temperature and not higher than 200 ° C, more preferably 180 ° C.
The following are preferred. The plasticizing temperature is controlled by adjusting the molecular weight, the degree of branching or the degree of polymerization of one or a mixture of two or more of polyethylene resin, polyurethane resin and polyester resin, which are the preferred main components of the coating film. it can.

On the other hand, if the plasticizing temperature of the resin (A) becomes too low, the coating film tends to become sticky or blocking during storage, transportation or handling. Therefore, the plasticizing temperature is 80 ° C. or higher, more preferably. It is desirable that the temperature be 100 ° C. or higher.

[Thermoplastic Resin (A) and Crosslinking Agent (B)
Thermal Crosslink Development Temperature] In the present invention, the reason why the thermal crosslink development temperature is set higher than the thermoplasticization temperature is as follows.
That is, in order to develop a high degree of bonding force by pressure bonding and heat baking of the coating film, and to exhibit a high level of high-temperature bonding force after bonding, corrosion resistance, solvent resistance, etc. Not only is it necessary to plasticize the resin mixture once to form a uniform bonding layer in the initial process of heating and baking after the surfaces of the adherends are aligned, but it is also necessary for the functional groups in the coating film resin to interact with each other. It is necessary to carry out a crosslinking reaction.

If this cross-linking reaction occurs in the manufacturing process of the resin-coated metal sheet, that is, in the coating / drying process, the amount of unreacted functional groups in the coating film at the time of baking and joining will be small and the amount of unreacted functional groups in the coating film will decrease. The cross-linking point (cross-linking density) does not rise sufficiently, and satisfactory adhesive strength cannot be obtained, and the resin coating film is less likely to be plasticized during baking and bonding, and bonding defects are likely to occur. Therefore, the temperature at which the resin coating film exhibits cross-linking reactivity for the first time in the baking and joining step must be higher than the coating / drying temperature when forming the coating film, and preferably about 100 ° C. or more, It should preferably be 120 ° C or higher.

However, in the case of a high temperature cross-linking reactive resin system having a cross-linking reactivity manifesting temperature exceeding 230 ° C., the baking temperature at the time of joining must be set to a high temperature exceeding 250 ° C. in consideration of productivity (joining efficiency). However, the resin constituting the coating film undergoes thermal decomposition during baking, making it difficult to obtain a substantially sufficient adhesive strength and causing deterioration of the appearance quality due to yellowing or the like at the non-bonded portion. Therefore, it is desirable that the temperature for exhibiting crosslinking reactivity is 230 ° C. or lower, and the more preferable upper limit temperature is about 180 ° C. for surely preventing thermal decomposition of the resin constituting the coating film.

[Type of thermoplastic resin (A)] Next, as the resin component of the thermoplastic resin (A) constituting the coating film, one or two kinds of polyethylene resin, polyurethane resin and polyester resin are used. The above is preferable. That is, the resin-coated metal sheet according to the present invention is usually subjected to processing such as cutting or molding before joining, but at this time, the resin coating film is also processed together with the metal base material. Therefore, it is important that the coating film itself as well as the metal base material is easily spread and deformed at the time of processing so that no flaws or defects occur on the surface. Therefore, in the present invention, in consideration of such workability before joining, a polyethylene-based resin that exhibits excellent spreadability and scratch resistance,
It is recommended to use one type or a mixture of two or more types of polyurethane resin and polyester resin.

[Type of cross-linking agent (B)] In order to exhibit the above-mentioned adhesiveness, high temperature bonding strength, corrosion resistance, solvent resistance, etc., as described above, the thermoplastic resin (A) in a heat-softened state is used. A cross-linking agent (B) which reacts with a reactive functional group contained therein at an appropriate cross-linking point is required, and the most preferable cross-linking agent (B) has a blocked isocyanate group. It is a melamine resin having a compound or a methylol group. Next, the crosslinking reaction between the thermoplastic resin (A) and the crosslinking agent (B) will be described.

[When the cross-linking agent (B) is an isocyanate group-containing compound] When the cross-linking agent (B) is an isocyanate group-containing compound, the functional group in the thermoplastic resin (A) for performing a cross-linking reaction with the isocyanate group. As a specific example of the group, a functional group having active hydrogen, for example, a hydroxyl group (—O
H), carboxyl group (-COOH), amino group (-N)
H ₂ ) and the like. Each of these functional groups having active hydrogen reacts with an active isocyanate group (-NCO group) generated by the removal of the protecting group from the protected isocyanate group to cause a crosslinking reaction, and the reaction is It is as follows. -NCO + -OH → -NH-COO- -NCO + -COOH → -NH-CO- + CO ₂ -NCO + -NH ₂ → -NH-CO-NH-

Among the functional groups having reactivity with the above isocyanate group, the amino group is particularly preferable. That is, the amino group has a higher crosslinking reaction rate with the isocyanate group than the hydroxyl group and the carboxyl group, and exhibits high adhesive strength in a shorter time or at a lower baking temperature.

By the way, the active isocyanate group easily reacts with a functional group containing active hydrogen such as a hydroxyl group, a carboxyl group and an amino group at room temperature, and therefore, a thermoplastic resin having a functional group having a reactivity with an isocyanate group in this form is used. When mixed and coexisted with the resin (A), the crosslinking reaction proceeds inside the coating layer even under storage temperature conditions, the crosslinking points gradually disappear, and the thermoplasticity of the coating becomes lost at the time of heating for baking. I will be raped. In such a resin coating film that has undergone a cross-linking reaction before baking and heating, even if the coating film surfaces are brought into close contact with each other and then baking is performed, the coating film does not plasticize and a uniform and smooth adhesive layer is formed. Since it is not obtained and the crosslinking reaction hardly occurs, the heat-sensitive adhesiveness intended in the present invention is not expressed.

Therefore, in the present invention, the isocyanate group contained in the cross-linking agent (B) in the coating film state before baking and heating is
It is necessary to previously protect the isocyanate group in the crosslinking agent (B) with a protective agent such as phenol, alcohol, oxime or active methylene so as not to react with the reactive functional group in the thermoplastic resin (A). is there. At this time, by appropriately selecting the type of the protective agent, it is possible to adjust the desorption temperature from the isocyanate group of the protective agent, and as described above, the thermal crosslinking reactivity expression temperature of the resin coating film is 100 to 230 ° C. ,
Desirably, it can be adjusted in the range of 120 to 200 ° C.

[When the cross-linking agent (B) is a melamine resin] The melamine resin recommended as one of the cross-linking agents (B) is a resin obtained by addition condensation of melamine and formaldehyde, and 1 in 1 molecule. It has ˜6 methylol groups (—NHCH ₂ OH). This methylol group is heated to give a hydroxyl group (-OH) or a carboxyl group (-).
It causes a cross-linking reaction with a functional group such as a COOH group), and the specific reaction is as follows. _{R-NHCH 2 OH + R'-} OH → R-NHCH 2 O-R '+ H 2 O → R-NH-R' + HCHO R-NHCH 2 OH + R'-COOH → R-NHCH 2 OCO-R ' + H ₂ O → R-NHCO-R '+ HCHO

[Preferred Thermoplastic Resin (A)] Thermoplastic Polyurethane Resin (A ₁ ) When a polyurethane resin is selected as the thermoplastic resin (A) used in the present invention, it is selected as the thermoplastic resin (A). A thermoplastic polyurethane resin (A ₁ ) having two or more functional groups showing crosslinking reactivity with an isocyanate group or a methylol group in one molecule is used. The thermoplastic polyurethane resin (A ₁ ) forms a strong coating film by a crosslinking reaction with a compound having two or more isocyanate groups or a crosslinking agent (B) having two or more methylol groups.

The thermoplastic polyurethane resin (A ₁ )
Examples of the production method include a compound having two or more functional groups (X ₁ ) having cross-linking reactivity with an isocyanate group or a methylol group, and two or more isocyanate groups (Y
_When a polyurethane resin is produced by reacting with an organic polyisocyanate compound having ₁ ), a functional group showing reactivity with an isocyanate group or a methylol group with respect to an isocyanate group (Y ₁ ) in an equivalent ratio of functional groups. Group (X
_By reacting ₁ ) in excess, a polyurethane resin (A ₁ ) having unreacted functional group (X ₁ ) can be obtained.

Thermoplastic Polyester Resin (A ₂ ) When a polyester resin is selected as the thermoplastic resin (A) used in the present invention, the thermoplastic resin (A) is crosslinked with an isocyanate group or a methylol group. A thermoplastic polyester resin (A ₂ ) having two or more functional groups showing reactivity in one molecule is used. The thermoplastic polyester resin (A ₂ ) forms a strong coating film by a crosslinking reaction with a compound having two or more isocyanate groups or a crosslinking agent (B) having two or more methylol groups.

The thermoplastic polyester resin (A ₂ )
The method for producing is a compound containing two or more hydroxyl groups (X ₂ ).
When a polyester-based resin is produced by reacting two or more carboxyl group-containing compounds (Y ₂ ) with a hydroxyl group (or a carboxyl group) in excess of the hydroxyl group (or a carboxyl group) in an equivalent ratio of functional groups. Having a compound (X
_{By using 2} ) and (Y ₂ ), a polyester resin (A ₂ ) having unreacted carboxyl groups (or hydroxyl groups) remaining can be obtained. Specific examples of the polyester-based resin thus obtained include glyptal resin, terephthalic acid-based resin, isophthalic acid-based resin, maleic acid-based resin, aliphatic polyester-based resin, oxyacid resin and the like.

Thermoplastic Polyethylene Resin (A ₃ ) When a polyethylene resin is selected as the thermoplastic resin (A) used in the present invention, the thermoplastic resin (A) is crosslinked with an isocyanate group or a methylol group. A thermoplastic polyethylene resin (A ₃ ) having two or more reactive functional groups in one molecule is used. The thermoplastic polyethylene resin (A ₃ ) forms a strong coating film by a crosslinking reaction with a compound having two or more isocyanate groups or a crosslinking agent (B) having two or more methylol groups.

The thermoplastic polyethylene resin (A ₃ )
Can be obtained by copolymerizing ethylene with an ethylenically unsaturated carboxylic acid having a carboxyl group.

In order to obtain a high-strength resin film necessary for improving abrasion resistance during punching and punching, punching workability, blackening resistance during working, etc., ethylenically unsaturated A carboxyl group-containing polyethylene-based resin obtained by copolymerizing carboxylic acid alone or an ethylenically unsaturated carboxylic acid with an acrylic ester or styrene with ethylene is preferably used.

Mixture of Two or More Thermoplastic Resins (A ₄ ) The thermoplastic resin (A) used in the present invention includes a polyurethane resin (A ₁ ), an ester resin (A ₂ ), a polyethylene resin ( It may be a mixture (A ₄ ) of two or more kinds of A ₃ ), in which case the thermoplastic resin (A) contains in one molecule a functional group showing crosslinking reactivity with an isocyanate group or a methylol group. A mixture (A ₄ ) of two or more thermoplastic resins is used. Specific combinations in that case include a mixture of polyurethane resin (A ₁ ) + polyester resin (A ₂ ), a mixture of polyester resin (A ₂ ) + polyethylene resin (A ₃ ), polyethylene resin ( A ₃₎ + polyurethane resin (A ₁₎
Or a mixture of polyurethane resin (A ₁ ) + polyester resin (A ₂ ) + polyethylene resin (A ₃ ).

[Structure of Crosslinking Agent (B)] Blocked isocyanate group-containing compound (B ₁ ) The blocked isocyanate group-containing material (B ₁ ) is obtained by reacting an organic polyisocyanate compound with a known blocking agent. To be At this time, the heat release temperature of the blocking agent from the isocyanate group can be adjusted to 100 to 200 ° C. by appropriately selecting the types of the organic polyisocyanate compound and the blocking agent. At this time, it is preferable to select a blocking agent having a boiling point equal to or higher than the thermal crosslinking reaction temperature so that the blocking agent released during the thermal crosslinking reaction does not boil and foam.

Examples of such blocking agents include phenols such as phenol and cresol; alcohols such as methanol, ethanol and butyl cellosolve; lactams such as ε-caprolactam; methylethylketoxime,
Examples of known blocking agents include oxime-based agents such as cyclohexanone oxime; active methylene-based agents such as dimethyl malonate and ethyl acetoacetate.

Melamine Resin (B ₂ ) The melamine resin (B ₂ ) is an alcohol-modified melamine resin obtained by modifying (etherifying) polymethylolmelamine produced by the addition reaction of melamine and formaldehyde with alcohol. Preferably, the free formaldehyde concentration of the final product is adjusted to 0.5% or less to effectively act as a water-soluble and high nonvolatile concentration cross-linking agent. This melamine resin has a thermal crosslinking temperature of 100 by changing the functional group equivalent ratio of the methylol group in the melamine resin to the functional group in the thermoplastic resin (A) that causes a crosslinking reaction with the methylol group in the melamine resin. It can be adjusted to ˜200 ° C.

[Thermoplastic Resin (A) and Crosslinking Agent (B)
Raw Material of Polyurethane Resin ] Raw Material of Polyurethane Resin Thermoplastic polyurethane resin (A having functional group reactive with isocyanate group or melamine resin)
_As a raw material for producing ₁ ), known polyvalent hydroxyl compounds (compounds having two or more hydroxyl groups in one molecule), polyvalent amino compounds (compounds having two or more amino groups in one molecule) ), And a polyvalent aminohydroxyl compound (a compound having two or more hydroxyl groups and an amino group in one molecule).

As the polyvalent hydroxyl compound, ethylene glycol, diethylene glycol, butanediol, propylene glycol, hexanediol, polypropylene glycol, 3-methyl-1,5-pentanediol, 1,4-cyclohexanedimethanol, dihydroxyethyl terephthalate, Polyhydric alcohols such as hydroquinone dihydroxyethyl ether trimethylolpropane, glycerin and pentaerythritol, the above polyhydric alcohols and alkylene derivatives such as bisphenol A, bisphenol S, hydrogenated bisphenol A and dibromobisphenol A, or the above polyhydric alcohols. Alcohols or their alkylene derivatives and polyvalent carboxylic acids,
Polyvalent carboxylic anhydride, ester compound synthesized from polyvalent carboxylic acid ester, further polycarbonate polyol, polytetramethylene glycol, polycaprolactone polyol, polybutadiene polyol, polythioether polyol, polyacetal polyol,
Examples thereof include polyol compounds such as castor oil polyol.

Examples of the polyvalent amino compound include ethylenediamine, propylenediamine, diethylenetriamine, hexylenediamine, triethylenetetramine, tetraethylenepetamine, isophoronediamine, xylylenediamine, diphenylmethanediamine and hydrogenated diphenylmethanediamine. Examples of the polyvalent aminohydroxyl compound include diethanolamine and 3-aminopropanol.

Raw Material for Polyester Resin As a raw material for producing a thermoplastic polyester resin (A ₂ ) having an isocyanate group or a functional group reactive with melamine, a known polyvalent hydroxyl compound (in one molecule) To 2) and a polybasic acid (compound having 2 or more carboxyl groups in one molecule).

Polybasic acids (compounds having two or more carboxyl groups in one molecule) and their anhydrides include phthalic anhydride, phthalic acid, terephthalic acid, isophthalic acid,
Examples thereof include tetrachlorophthalic anhydride, succinic acid, adipic acid, sevanic acid, azelaic acid, and hexahydrophthalic anhydride. As the raw material, an intramolecular condensate of oxyacid, an unsaturated polybasic acid, or the like can be shared.
In addition, a small amount of monobasic acid (for example, benzoic acid) can be added to control the hardness and molecular weight of the coating film.

Examples of the polyvalent hydroxyl compound (compound having two or more hydroxyl groups in one molecule) include ethylene glycol, propylene glycol, diethylene glycol, glycerin, 1,3-butylene glycol, neopentyl glycol, trimethylolpropane and penta. Examples thereof include erythritol, sorbitol, butenediol, 4-hydroxyethoxyphenylpropane, glycerin monoallyl and the like.

Raw material for polyethylene resin A thermoplastic polyethylene resin (A having a functional group reactive with an isocyanate group or a melamine resin)
_As the raw material for producing ₃ ), ethylene and one or more ethylenically unsaturated carboxylic acids such as (meth) acrylic acid, maleic acid and itaconic acid are used. Besides ethylenically unsaturated carboxylic acid, for example, methyl (meth) acrylate, ethyl (meth) acrylate,
(Meth) acrylic acid esters such as propyl (meth) acrylate, styrene-based monomers such as styrene, vinyltoluene, chlorostyrene, hydroxyethyl (meth) acrylate, (meth) hydroxy such as (meth) acrylhydroxypropyl One or more kinds of alkyl, N-substituted (meth) acrylamide such as N-methylol (meth) acrylamide, epoxy group-containing (meth) acrylic acid ester such as (meth) acrylglycidyl, and (meth) acrylonitrile. Can be used together.

Of the blocked isocyanate group-containing compound
As the organic polyisocyanate compound used as a raw material for producing the raw material blocked isocyanate group-containing compound (B ₁ ), an aromatic or alicyclic isocyanate compound may be used alone or in combination of two or more. Specific examples include tolylene diisocyanate, diphenylmethane diisocyanate, xylylene diisocyanate, naphthylene diisocyanate, isophorone diisocyanate,
Isocyanates such as hexamethylene diisocyanate, hydrogenated diphenylmethane diisocyanate, hydrogenated toluene diisocyanate and tetramethylene xylylene diisocyanate; and buret compounds and isocyanurate compounds of the above isocyanates, and the above isocyanates such as trimethylolpropane Examples thereof include compounds obtained by addition reaction with a hydroxy compound.

Raw Materials for Melamine Resin Examples of the raw materials for producing the melamine resin (B ₂ ) include melamine and formaldehyde, and alcohols such as methanol, ethanol, propanol and butanol used for modification. To be

[Thermoplastic Resin (A) and Crosslinking Agent (B)
Hydrophilicity imparting method] to the above thermoplastic polyurethane resin
(A₁ ), Thermoplastic polyester resin (A ₂ ), Heat
Plastic polyethylene resin (A₃ ), Blocked isocyanate
Nate group-containing compound (B₁ ), Melamine resin (B₂ )
At the time of production, anionic hydrophilic groups and
A hydrophilic hydrophilic group, non-ionic hydrophilic group, etc.
Contains a surfactant in the reaction system, and these thermoplastic resins
(A₁ ), (A₂ ), (A₃ ) Or cross-linking agent (B₁ ), (B
₂ ) Can be made hydrophilic and applied as an aqueous resin liquid
It will be possible.

[Favorability of thermoplastic resin (A) and crosslinking agent (B)
Good mixing ratio] Reactive with the above isocyanate groups
Functional group-containing polyurethane resin (A ₁ ), Polyeste
Resin (A₂ ), Polyethylene resin (A₃ )
Or a compound containing two or more blocked isocyanate groups
Thing (B₁ ) And a preferable mixing ratio is
The functional group that reacts with
In terms of equivalent ratio with the quaternized isocyanate group, it is 1: 0.5 to 1.
2, more preferably in the range of 1: 0.8 to 1: 1.5
It

Further, one or more kinds of functional group-containing polyurethane resin (A ₁ ), polyester resin (A ₂ ), polyethylene resin (A ₃ ) having reactivity with the melamine resin and melamine resin. The preferable blending ratio of (B ₂ ) is 100: 2 to 100: 30 by weight, and more preferably 100: 10 to 100: 20.

The reason is that the above-mentioned thermoplastic resin (A ₁ ),
One or more of (A ₂ ), (A ₃ ) and a crosslinking agent (B
_{When 1} ) and (B ₂ ) are mixed to synthesize a resin liquid, if the ratio is out of the above-mentioned preferable mixing ratio, an active isocyanate group or an uncrosslinked melamine resin in the molecule of the obtained mixed resin after baking treatment, or This is because a large amount of functional groups reactive with these will remain, resulting in insufficient heat-resistant adhesion and solvent resistance after baking and heat treatment.

The paint containing the thermoplastic resin (A) and the cross-linking agent (B) thus obtained is uniformly applied to the surface of the metal plate, and the temperature conditions are such that these (A) and (B) do not cause a cross-linking reaction. , Usually 30 to 100 ° C., preferably 60 to
When dried at 80 ° C., the heat-sensitive adhesive resin-coated metal plate of the present invention is obtained.

[Preferred Coating Amount of Resin Coating] The coating amount of the above coating film is 0.5 g / m ² or more, preferably 1 or more, as the coating amount after drying for the purpose of ensuring sufficient adhesive strength.
It should be at least g / m ² . However, when the coating film adhesion amount is less than 0.5 g / m ² , the surface of the metal plate cannot be sufficiently covered with the coating film, so that the resin coating film during baking is difficult to be uniform and smooth, and partially This is because a defective joint is likely to occur.

The upper limit of the coating amount of the resin coating film is not particularly limited from the viewpoint of adhesive strength, but not only the coating amount becomes too thick and the cost of coating material per unit treated area becomes high, The drying time after application of the resin liquid also becomes long, the line speed becomes slow in particular in the continuous manufacturing process in the continuous coating line, the productivity decreases, and as a result, the manufacturing cost increases. Therefore, the amount of resin coating adhered is 30g
/ M ² or less is good. From the viewpoints of both adhesiveness and manufacturing cost, the more desirable adhesion amount of the resin coating film is 1 to 10 g /
It is in the range of m ² .

[Acceptable Modification of Additives and Resin Components] In preparing a coating solution containing the above-mentioned thermoplastic resin (A) and crosslinking agent (B), the thermosensitive adhesive performance exhibited by them is not impaired. In the range, partial crosslinking agent, diluting solvent, anti-skin agent, leveling agent, defoaming agent, penetrating agent,
Various additives such as film-forming aids, color pigments, thickeners, etc., or fine powder silica for improving adhesion and corrosion resistance, colloidal silica, silane coupling agents, etc. are added in appropriate amounts as necessary to improve coating performance. It is possible to raise it further.

In order to improve weather resistance, hardness, shear strength, etc. of the coating film, a part of the thermoplastic resin (A) is modified with acrylic resin or epoxy resin, and the cost of the resin is reduced. It is also possible to mix various resins such as polyvinyl alcohol resin, SBR resin, chloroprene resin, NBR resin, acrylic resin, vinyl chloride resin, vinyl acetate resin, ethylene / vinyl acetate resin, etc., in an amount that does not impair the heat-sensitive adhesive performance. Is.

[Manufacturing Method] Next, a method of manufacturing the heat-sensitive adhesive resin-coated metal plate according to the present invention will be described. This resin-coated metal plate is prepared by applying the aqueous coating solution containing the above-mentioned thermoplastic resin (A) and crosslinking agent (B) as main components to the surface of the metal plate by an arbitrary coating method and drying the metal plate surface. However, by setting the drying temperature at this time to below the temperature at which the crosslinking reactivity develops (below the release temperature of the blocking agent or the thermal crosslinking temperature of the melamine resin), the surface of the coating after drying the resin coating becomes tacky. It is possible to form a coating film which does not cause blocking or blocking, and which is a hard film that hardly scratches during processing such as slitting or punching, and has thermal crosslinking reactivity.

At this time, if the coating film is dried at a temperature exceeding the thermal crosslinkability manifesting temperature, no problem occurs in the film formation itself, but the curing reaction by the crosslinking agent in the coating film proceeds in the drying step. However, the thermoplasticity of the coating film is lost during the subsequent baking and joining, and the amount of residual functional groups (crosslinking points) in the coating film also decreases, resulting in the failure to obtain a high degree of bonding strength. That is, when a melamine resin is used as the crosslinking agent (B), the reaction between the melamine resin and the functional group in the thermoplastic resin (A) proceeds, and when a blocked isocyanate is used as the crosslinking agent, The blocking agent of the blocked isocyanate group causes a separation reaction to regenerate the active isocyanate group having high reactivity into the coating film, and the reaction between the active isocyanate group and the functional group in the thermoplastic resin (A) occurs. When these reactions proceed in the drying / film forming process, the thermoplasticity of the coating film is lost in the subsequent initial heating process for bake bonding, and the amount of functional groups (crosslinking points) in the coating film also decreases, resulting in As a result, it becomes impossible to obtain high adhesive strength at the joint.

For these reasons, the drying temperature for coating / film formation of the coating liquid containing the thermoplastic resin (A) and the cross-linking agent (B) is lower than the temperature at which the heat-crosslinking reactivity is exhibited (desorption temperature of the blocking agent or melamine). The temperature must be below the thermal crosslinking reaction temperature of the resin). If a sufficient cooling step cannot be provided immediately after drying and film formation, if the film is dried at a temperature lower than the plasticizing temperature of the resin constituting the coating film, blocking or the like does not occur even when wound as a coil product. preferable.

When the heat-sensitive adhesive resin-coated metal sheet of the present invention is processed into a predetermined shape and then the portions to be joined are overlapped and joined, the heating temperature (baking temperature) is set to the thermoplasticity. High adhesive strength can be obtained by setting the temperature above the thermoplasticization temperature of the resin (A) and above the temperature at which the resin (A) and the cross-linking agent (B) exhibit cross-linking reactivity above 250 ° C. . However, when the baking temperature is lower than the crosslinking reactivity expression temperature (blocking agent release temperature or melamine resin thermal crosslinking reaction temperature), the crosslinking agent (B) contained in the coating film contains a blocked isocyanate group. When it is the compound (B ₁ ), the blocking agent does not separate from the blocked isocyanate group and the active isocyanate group is not regenerated, and the crosslinking agent (B) contained in the coating film is a melamine resin ( When it is B ₂ ), a cross-linking reaction between the functional group having reactivity with the melamine resin and the methylol group in the melamine resin does not occur, so that a cross-linking point with the functional group cannot be formed, resulting in sufficient adhesive strength. Can't get

On the other hand, when the baking temperature is lower than the thermoplasticity developing temperature, the fluidity of the resin in the initial process of baking and heating is poor and the leveling effect cannot be obtained, so that a uniform adhesive layer is not formed and the intended adhesion is achieved. No strength can be obtained.

Furthermore, when the baking temperature is higher than 250 ° C., when the compound (B ₁ ) having a blocked isocyanate group is used as the crosslinking agent (B), the regeneration of the isocyanate group proceeds sufficiently, Further, when the melamine resin (B ₂ ) is used, the crosslinking reaction with the functional group also actively progresses, but on the other hand, the thermal decomposition of the resin progresses to cause the deterioration of the coating film component and the adhesive strength. However, not only does the resin show a declining tendency, but also yellowing due to the decomposition of the resin progresses and the appearance may deteriorate.

For the above reason, the baking temperature for adhesion is not less than the thermoplasticizing temperature of the thermoplastic resin (A), and the thermal crosslinking reactivity of the thermoplastic resin (A) and the crosslinking agent (B) is expressed. It should be above the temperature and below 250 ° C, preferably below 200 ° C. By the way, in carrying out the present invention, the coating film-constituting resin is used as a water-dispersible or water-soluble coating liquid, and the advantages brought by it are as follows.

That is, if it is a water-based resin, it is not necessary to provide a special exhaust treatment facility for removing a volatile organic solvent generated when a solvent-based resin liquid is used in a resin coating line, and avoid an increase in facility cost. Because you can Further, as the resin liquid coating equipment used when carrying out the present invention, for example, when using a plated metal plate or a chemical conversion treatment metal plate as an original plate, install the resin coating equipment in an existing plating treatment or chemical conversion treatment line. It only needs to be provided, and it is possible to enjoy the advantage that the productivity is improved as compared with the case of manufacturing with a dedicated resin coating line provided with a special exhaust treatment facility.

When the coating solution is of an organic solvent type, the solid content concentration and viscosity of the coating solution are liable to change with time due to the evaporation of the solvent, which makes it difficult to control the amount of the coating film to be applied and also to apply the coating solution. Unevenness is also likely to occur. However, when the coating liquid is water-dispersible or water-soluble, the evaporation from the coating liquid is extremely small, so that the solid content concentration and the viscosity do not change with time, stable coating properties can be obtained, and the amount of adhesion can be easily controlled. Become.

By the way, the coating method of the resin-containing coating solution on the metal surface is not limited at all, but as a general method, for example, the surface is cleaned or pretreatment (for example, phosphate treatment, chromate treatment). Examples of the method include applying a resin diluting solution to the surface of a metal plate or a long metal band that has been subjected to the above, using a roll coater method, a spray method, a curtain flow coater method, or the like. However, the method of coating with a roll coater is most preferable in view of the uniformity of coating film thickness, treatment cost, coating efficiency and the like.
The resin coating film can be formed on only one side or both sides of the metal plate.

The type of base metal plate used in the present invention is not limited at all, and various alloy steel plates such as the most common mild steel plates and stainless steel plates, as well as Al and Al alloy plates, Cu and Cu alloy plates are used. , Ti and Ti alloy plates,
Plated metal plate (zinc and zinc alloy-based plated steel plate, Al
And Al alloy-based plated steel sheets, copper-based plated steel sheets, Ni-based plated steel sheets, Cr-based plated steel sheets, various plated metal sheets such as zinc-plated Al and Al alloy sheets), chemical conversion treatment (phosphate treatment, chromate treatment, etc.) metal It can be widely used for plates, as well as painted metal plates.

The heat-sensitive adhesive resin-coated metal sheet of the present invention thus obtained is widely used as described above for automobiles, home electric appliances, outer panel materials for metal furniture, building materials, etc. At the time before or after laminated joining, for example, acrylic resin paints, melamine resin paints, polyester resin paints, etc. are sprayed, electrostatically applied, electrodeposited, etc. on parts other than the joining surface. It is also possible to paint by various coating methods.

For example, the resin-coated metal plate of the present invention is punched into a predetermined shape, two sheets are caulked, and then the above-mentioned coating solution is applied to the surface to carry out incomplete baking treatment, and the top-coat paint is baked. It is also possible to utilize the heat of the time to cause a crosslinking reaction of the heat-sensitive adhesive resin coating film at the same time, and to develop a high degree of adhesive strength at the joint. That is, if such a method is adopted, it is possible to enjoy the advantage that the baking of the top coating film and the joining of the heat-sensitive adhesive coating film by the crosslinking reaction can be performed at the same time.

[0079]

EXAMPLES The constitutions and effects of the present invention will be specifically described below with reference to examples, but the present invention is not limited by the following examples and can be adapted to the gist of the preceding and the following. It is of course possible to appropriately change and implement the range, and all of them are technically included in the present invention.

Example 1 The following organic compounds were used as raw materials for preparing a resin coating solution for coating a metal plate. 1. Hydroxyl group-containing polyurethane resin (a): Functional group content (solid content) 20 to 30 KOH mg / g, molecular weight 50.0
00-200,000 2. Hydroxyl group-containing polyester resin (b): Functional group content (solid content) 20 to 30 KOH mg / g, molecular weight 50.0
00-200,000 3. 3. Carboxyl group-containing polyurethane resin (c): Functional group content (solid content) 20 to 30 KOH mg / g, molecular weight 50,000 to 200,000 4. 4. Carboxyl group-containing polyethylene resin (d): Functional group content (solid content) 20 to 30 KOH mg / g, molecular weight 50,000 to 200,000 5. Carboxyl group-containing polyester resin (e): Functional group content (solid content conversion) 20 to 30 KOH mg / g, molecular weight 50,000 to 200,000 6. Amino group-containing polyurethane resin (f): Functional group content (solid content conversion) 20 to 30 KOH mg / g, molecular weight 50,
000-200,000 7. Amino group-containing polyurethane resin, carboxyl group-containing polyethylene resin, hydroxyl group-containing polyester resin (g): Functional group content (solid content conversion) 20 to 30 KOH m
g / g, molecular weight 50,000-200,000 8. Blocked isocyanate group-containing organic compound (h):
Functional group content (converted to solid content) 1 to 20% by weight (converted as NCO), molecular weight 200 to 600 9. Melamine resin (i): Functional group content (solid content conversion) 3
5 to 55% by weight (converted as NH ₂ CH ₂ OH), molecular weight 200
~ 600

As a comparative synthesis example, a thermoplastic resin containing no functional group necessary for causing a thermal crosslinking reaction was also used. 10. Polyurethane-based resin (j) containing no functional group showing reactivity with isocyanate group: functional group content (in terms of solid content) 0 KOH mg / g, molecular weight 50,000 to 200,0
00 11. Polyethylene resin (k) containing no functional group reactive with isocyanate group: Functional group content (solid content conversion) 0 KOH mg / g, molecular weight 50,000-200,00
0 12. Polyester resin (l) containing no functional group showing reactivity with isocyanate group: Functional group content (solid content) 0 KOH mg / g, molecular weight 50,000 to 200,00
0 13. Polyurethane resin (m) that does not contain a functional group that reacts with melamine resin: Functional group content (solid content conversion)
0 KOH mg / g, molecular weight 50,000-200,000 14. Polyethylene resin (n) containing no functional group which reacts with melamine resin: Functional group content (solid content conversion) 0
KOH mg / g, molecular weight 50,000-200,000 15. Polyester resin that does not contain a functional group that is reactive with melamine resin (o): Functional group content (solid content conversion)
0 KOH mg / g, molecular weight 50,000 to 200,000 The above-mentioned various organic compounds (a) to (o) are blended in the ratios shown in Table 1 below, and coating liquids A to M for coating on a metal plate. Was produced.

Among the various coating liquids shown in Table 1, N
o. Regarding A to G, the equivalent ratio of regenerated isocyanate group / active hydrogen group contained in the resin or the equivalent ratio of the functional group showing reactivity with the melamine resin and the melamine resin is adjusted within an appropriate range, On the other hand, No. Regarding H to M, one of them does not have a functional group and has thermoplasticity but does not have thermal crosslinkability. Moreover, the thermoplasticization temperature and the thermal crosslinking property development temperature shown in Table 1 refer to the values measured by the following methods.

[Measurement Method of Thermoplasticization Temperature] The temperature at which the film obtained by drying the resin liquid on a Teflon plate at 80 ° C. is melted on the hot plate heated to a predetermined temperature is measured to determine the thermoplasticization temperature. And [Measurement Method of Thermal Crosslinking Development Temperature] The film obtained by drying the resin liquid on a Teflon plate at 80 ° C. was subjected to differential thermal analysis to measure the desorption temperature of the protective agent, which was defined as the thermal crosslinking development temperature.

[0084]

[Table 1]

Next, coating type chromate treatment (chromate adhesion amount: 50 mg / m ² ) was applied to the surface of the electric pure Zn-plated steel plate (plating adhesion amount: 20 g / m ² , plate thickness 0.6 mm).
Was applied, and this was used as a treated metal plate for resin application. After coating various coating liquids A to M shown in Table 1 with a predetermined film thickness on the surface of the metal plate to be treated, the resin was heated at a predetermined plate temperature (drying temperature) while being transferred in a hot air drying oven. After the coating film was dried and formed into a film, the various resin-coated steel sheets obtained were subjected to a coating film performance evaluation test by the following method.

1. Performance evaluation after coating-drying (before baking) (1) Scratch resistance (coating hardness) In order to investigate the coating film hardness of the coating metal plate after coating-drying of the resin liquid, it is specified in JIS-K5400. A pencil hardness test was carried out to evaluate the scratch resistance of the coating film surface. The judgment is
The coating film surface was scratched a total of 5 times with pencils of various hardness, and the pencil hardness one rank below with two or more scratches was defined as the coating film hardness. The evaluation criteria are as follows. <Scratch resistance> ◎ Excellent: Pencil hardness H or higher ○ Good: 〃 HB to F × Poor: 〃 B or less

(2) Corrosion resistance (white rust resistance) Application of resin liquid-corrosion resistance of a coated metal plate after drying is determined by JIS-
It was subjected to the 5 wt% salt spray test shown in Z2371, and the corrosion resistance was evaluated by the white rust resistance. That is, it was evaluated by the 1% white rust generation time due to the corrosion of the electric pure Zn plating layer under the coating film. The evaluation criteria are as follows. <White rust resistance> ◎ Excellent: White rust occurs at 240 h or more ○ Good: White rust occurs at 120 to 240 h △ Slightly inferior: White rust occurs at 48 to 120 h × Poor: White rust occurs within 48 h

2. Performance evaluation after baking (3) Self-adhesiveness (heat-sensitive self-adhesive strength) Application of resin liquid-coated metal plate after drying 25 mm x 100
After cutting to a size of 25 mm, the coated surfaces are 25 mm x 1
A simple laminated material (single lap joint) was produced by superposing them in an area of 2 mm. This laminated material is heated with a predetermined temperature (bonding temperature) using a hot press machine to
After pressurizing (3 kgf / cm ² ) for 0 minutes and then cooling, the obtained test piece is subjected to a constant temperature and constant humidity test under the conditions shown below according to JIS K-6857, and then the same as the above (3). The durability of the adhesive strength (aging deterioration of the adhesiveness) was investigated by conducting a uniaxial tensile test.

[Constant temperature and humidity test] Temperature: 25 ° C., relative humidity: 90% RH, test time: 72
The 0h evaluation standard is as follows. <White rust resistance> ◎ Excellent: Adhesive strength 130 kgf / cm ² ○ Good: 〃 70 to 130 kgf / cm ² △ Slightly inferior: 〃 40 to 70 kgf / cm ² × Inferior: 〃 less than 40 kgf / cm ²

(4) Heat-resistant adhesiveness Coating of resin solution-dried coated metal plate 30 mm × 75 m
Cut to m size and the coating surfaces are 30mm x 10mm
A simple laminated material (single lap joint) was produced by superimposing it in the area of. This laminated material was pressed (3 kgf / cm ² ) for 20 minutes using a heating press device at a predetermined temperature (bonding temperature) and then cooled, and the obtained test piece was placed in an atmosphere of 60 ° C. The same uniaxial tensile test as in (3) above was performed to examine the adhesive strength (heat resistant adhesiveness) in a high temperature environment. The evaluation criteria are as follows. <Heat resistant adhesion> ◎ Excellent: Adhesive strength of 80 kgf / cm ² or more ○ Good: 〃 50 to 80 kgf / cm ² × Poor: 〃 less than 50 kgf / cm ²

(5) Corrosion resistance (white rust resistance) In order to evaluate the corrosion resistance after baking, first, the coated metal plate after resin solution application and drying was cut into a size of 70 mm × 150 mm, and at the predetermined temperature shown in Table 2. After heating and baking, and tape-sealing the end surface and the back surface, it was subjected to a 5 wt% salt water spray test shown in JIS-Z2371 in the same manner as in (2) above. The corrosion resistance was evaluated by the white rust resistance, that is, the 1% white rust generation time due to the corrosion of the electric pure Zn plating layer under the coating film. The evaluation criteria are as follows. <White rust resistance> ◎ Excellent: White rust occurs at 240 h or more ○ Good: White rust occurs at 120 to 240 h △ Slightly inferior: White rust occurs at 48 to 120 h × Poor: White rust occurs within 48 h

(6) Solvent resistance In order to evaluate the solvent resistance of the resin coating film after heating and baking, first, the coated metal plate after resin solution application and drying was 70 mm × 150 mm.
The sample was cut into a size of mm, heated and baked at a predetermined temperature shown in Table 2, and gauze impregnated with toluene was slid 20 times on the surface of the obtained test piece to evaluate the deterioration state of the coating film. The evaluation criteria are as follows. <Solvent resistance> ◎ Excellent: No abnormalities ○ Good: Slightly swelling degree × Inferior: Dissolution of coating film The above performance evaluation test results are shown in Tables 2 to 9, and the results are considered as follows. be able to.

A coated steel sheet obtained by forming coating films using the coating solutions A to G having the functional groups defined in the present invention in a predetermined equivalent ratio at the preferable deposition amount, drying temperature and baking temperature defined in the present invention is , Excellent scratch resistance and corrosion resistance (both performance after drying) and self-adhesiveness, adhesiveness with cloth, adhesive durability,
It can be seen that it has heat resistant adhesion, corrosion resistance, and solvent resistance (after heating and baking).

On the other hand, those without a coating film (No. 11)
Is inferior to all performance. Even when the coating solutions A to G satisfying the conditions specified in the present invention are used, if the drying temperature specified in the present invention exceeds the thermal crosslinkability manifesting temperature of the resin, the heating and baking temperature is specified. Outside the temperature range, there are many micro defects such as pinholes on the surface of the coating film, a uniform and smooth adhesive layer is not formed during baking, there are few crosslinking points, and the crosslinking reaction has already progressed during film formation. , Due to insufficient crosslinking reaction during baking, thermal deterioration of coating film during baking, etc., corrosion resistance (performance after drying and baking), self-adhesiveness, adhesion to cloth,
It can be seen that one or more of the high temperature adhesiveness and solvent resistance (performance after baking) are inferior. Further, when the amount is less than the preferable amount defined in the present invention (reference example), the amount of the adhesive layer is insufficient, or non-uniform adhesion occurs.
Both performances are poor.

In particular, when the coating film is dried at a high temperature, the cross-linking reaction with the active hydrogen group in the coating film or the melamine resin cross-linking reaction due to the elimination of the isocyanate group protected during the drying for film formation. Occurs, since the thermoplasticity of the coating film disappears due to the curing reaction of the resin, even if the coating film is heated and baked thereafter, the integration and cross-linking reaction of the adhesive surfaces between the coating surface surfaces hardly occur, and in the present invention, The intended heat-sensitive adhesiveness cannot be obtained.

Regarding the coating liquids H to M, as described above, since the thermoplastic resin in the coating liquid does not have an isocyanate group or a functional group showing reactivity with a melamine resin, the coating film is baked. However, even if it is carried out, only adhesion by melt integration by thermoplasticization can be obtained, and high adhesive strength due to a crosslinking reaction in the coating film adhesive layer cannot be obtained. Further, since the adhesive layer in this case has the same thermoplasticity as that before the baking even after the baking, it is understood that the performances such as the high temperature adhesiveness and the solvent resistance after the baking are insufficient.

[0097]

[Table 2]

[0098]

[Table 3]

[0099]

[Table 4]

[0100]

[Table 5]

[0101]

[Table 6]

[0102]

[Table 7]

[0103]

[Table 8]

[0104]

[Table 9]

Example 2 Electrically pure galvanized steel strip (coating weight: 20 g / m ² ,
A coating type chromate treatment (chromate adhesion amount: 50 mg / m ² ) was applied to the surface of a plate thickness of 0.6 mm), and this was used as a treated metal steel strip for resin coating. On the surface of the metal steel strip to be treated, the following water-based resin coating liquid X and solvent-based resin coating liquid Y
Roll dry with a roll coater to a predetermined thickness (5.0 g /
m ² ), and the variation of the dry film thickness per coating length of the metal steel strip at this time was examined. The results are shown in Fig. 1. 1. Water dispersion type (polyurethane resin-melamine resin) coating solution X 2. Solvent type (polyurethane resin-melamine resin) coating liquid Y

As is clear from FIG. 1, in the case of the water dispersion type resin coating liquid X, the target coating film thickness is ± 0.2.
Only g / m ² fluctuates. On the other hand, in the case of the solvent-based resin liquid Y, the resin solid content concentration and the viscosity of the coating liquid started to increase from the beginning of the coating due to the evaporation of the solvent, and the dry coating film thickness increased accordingly. The resin solid content concentration and viscosity were adjusted by addition, but the maximum thickness of the dry coating film varied by 0.9 g / m ² .

[0107]

EFFECTS OF THE INVENTION Since the present invention is constituted as described above, it does not have stickiness or blocking property in a dry state, and the film is not scratched by slitting or punching, and the coating layer is formed. After the heat-baking treatment and the crosslinking reaction, it is possible to provide a resin-coated metal sheet that can exhibit excellent adhesiveness, adhesive durability, high-temperature adhesiveness, solvent resistance, corrosion resistance, and the like.

[Brief description of drawings]

FIG. 1 is a graph showing the amount of variation in the dry coating film thickness in the longitudinal direction of a metal strip, when the aqueous dispersion type resin coating liquid is used and when the solvent type resin coating liquid is used.

Continuation of the front page (51) Int.Cl. ⁶ Identification code Office reference number FI Technical display location B32B 27/06 B32B 27/06 27/18 27/18 Z 27/40 27/40

Claims (7)

[Claims] 1. A surface of a metal plate is coated with a coating film containing a water-soluble or water-dispersible thermoplastic resin (A) having a reactive functional group and a cross-linking agent (B). Characteristic heat-sensitive adhesive resin coated metal plate. 2. The thermoplastic resin (A) has one or two kinds of a polyethylene resin, a polyester resin and a polyurethane resin having a functional group showing reactivity with a melamine resin or an isocyanate group. The heat-sensitive adhesive resin-coated metal sheet according to claim 1, wherein the crosslinking agent (B) is composed of a melamine resin having an active methylol group or a blocked isocyanate group-containing compound. 3. The functional group showing reactivity with a melamine resin is a hydroxyl group and / or a carboxyl group, and the functional group showing reactivity with an isocyanate group is selected from the group consisting of a hydroxyl group, an amino group and a carboxyl group. The heat-sensitive adhesive resin-coated metal plate according to claim 2, which is one kind or two or more kinds. 4. The thermoplastic resin (A) is plasticized in a temperature range of 80 to 200 ° C., and the thermoplastic resin (A) and the cross-linking agent (B) are the plasticizing temperature of the thermoplastic resin (A). The heat-sensitive adhesive resin-coated metal plate according to any one of claims 1 to 3, which undergoes a crosslinking reaction in the temperature range of 230 ° C or lower. 5. The adhesion amount of a coating film containing a thermoplastic resin (A) and a cross-linking agent (B) is 0.5 to 60 g / m ^{2 in} terms of solid content.
The heat-sensitive adhesive resin-coated metal plate according to any one of claims 1 to 4. 6. A coating solution containing the thermoplastic resin (A) according to any one of claims 1 to 5 and a cross-linking agent (B) is applied to the surface of a metal plate, and then (A) and (B). A method for producing a heat-sensitive adhesive resin-coated metal plate, which comprises drying to form a film under a temperature condition that does not cause a crosslinking reaction. 7. The heat-sensitive adhesive resin-coated metal plates according to claim 1, or the heat-sensitive adhesive resin-coated metal plates and other adherends are overlapped to form a thermoplastic resin (A). A temperature at which the coating film containing the crosslinking agent (B) causes a crosslinking reaction,
A method for joining a heat-sensitive adhesive resin-coated metal sheet, which comprises baking and joining at a temperature of 250 ° C. or less.